Microstructured extracellular matrices in tissue
engineering and development
Celeste M Nelson1 and Joe Tien2
Microscale heterogeneity in the extracellular matrix (ECM)
provides spatial information that allows tissues to develop and
function properly in vivo. This heterogeneity in composition
(chemistry) and structure (geometry) creates distinct
microenvironments for the cells that comprise a tissue. In
response, populations of cells can coordinate their behaviors
across micrometer-to-millimeter length scales to function as a
unified whole. We believe techniques to mimic the microscale
heterogeneity of the ECM in vitro will revolutionize studies that
examine how large groups of cells interact. Micropatterned
ECMs used for engineering perfused microvascular networks
and functional epidermis and for understanding symmetrybreaking events in epithelial morphogenesis illustrate potential
applications in tissue engineering and development.
Addresses
1
Life Sciences Division, Lawrence Berkeley National Laboratory,
Berkeley, CA 94720, USA
2
Department of Biomedical Engineering, Boston University, Boston,
MA 02215, USA
Corresponding authors: Nelson, Celeste M (cmnelson@lbl.gov);
Tien, Joe (jtien@bu.edu)
Current Opinion in Biotechnology 2006, 17:518–523
This review comes from a themed issue on
Tissue and cell engineering
Edited by James L Sherley
Available online 12th September 2006
0958-1669/$ – see front matter
# 2006 Elsevier Ltd. All rights reserved.
DOI 10.1016/j.copbio.2006.08.011
Introduction
The extracellular matrix (ECM) environments of most
tissues and organs are inherently heterogeneous [1]. This
heterogeneity, whether chemical or structural in nature, is
critical for proper tissue form and function. For example, a
dense basal lamina that separates epithelial and endothelial cells from the underlying interstitial ECM is required
for correct cellular polarity and differentiation [2]. Likewise, periodic or fractal ECM geometries are needed for
efficient transport in absorptive and secretory tissues [3].
For the past thirty years, investigations of the behavior of
cultured cells and tissues have relied heavily on the use of
homogeneous two-dimensional (2D) and three-dimensional (3D) ECMs. Although these systems have shed
light on the basic biology of cell adhesion, the differences
between normal and malignant cells, and the mechanisms
underlying tissue-specific gene expression [4], they
Current Opinion in Biotechnology 2006, 17:518–523
cannot replicate the complex structure of ECMs in vivo,
in which bends, folds, channels and branches — at the
size scale of groups of cells — are plentiful [5]. Thus, the
cooperative behavior of cells across large length scales
(e.g. in morphogenesis, physiology and tissue engineering) has been nearly impossible to study in vitro, other
than with explanted tissues.
What if researchers could create artificial ECMs that
replicate the heterogeneity of native ones? For example,
what if one could engineer a collagen gel so that it
contained a branching network that mimicked the scale
and shape of actual glands in vivo? What studies would
these designer ECMs enable? This review describes
recent uses of microstructured ECMs (ECMs that possess
texture at the 5–1000 mm scale) in tissue engineering and
studies of development, and provides evidence that cells
grown in these ECMs exhibit unique behaviors not present in homogeneous cultures. Examples of microstructured ECMs designed for microvascular and epidermal
tissue engineering and for recapitulation of epithelial
development in vitro illustrate these ideas.
Why introduce structure into ECMs?
Traditional view: dominance of chemistry
The ECM consists of glycoproteins (such as collagen,
fibronectin and laminin), proteoglycans and glycosaminoglycans that undergo self-assembly as well as cell-directed
assembly to form a complex organized meshwork [6].
Besides serving as a scaffold to which cells adhere, ECMs
act as reservoirs that sequester and release growth factors
and other molecules that affect cellular behavior [7].
ECM molecules and their receptors are required during
development, because null mutations in either generally
lead to embryonic or perinatal lethality, or to severe
abnormalities shortly after birth [8,9]. Many ECMs also
play central roles in homeostasis [2], wound repair [10],
and diseases such as atherosclerosis [11] and cancer
[12,13], partly through mechanical alterations [14].
Whereas the composition and structure of the ECM varies
depending on the tissue and organ, in general ECMs are
compliant viscoelastic materials with bulk properties of
hydrogels [15]. Reconstitution of ECMs in vitro often
proceeds by gelation of a liquid mixture of collagens and
other proteins; hence, the final gels are invariably homogeneous at the micrometer scale (although not at the
nanometer scale) [16,17]. Extensive studies of cellular
behavior in these homogeneous gels have understandably
favored the view that biochemical composition plays the
dominant role in ECM functionality.
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Extracellular matrix applications Nelson and Tien 519
Emerging view: importance of form
Figure 1
In contrast to the bulk hydrogels traditionally used in
culture models, ECMs within native tissues contain as
much architecture as their constituent cells. Organs are
built of tissues in which the cells and ECMs take the form
of sheets (e.g. squamous epithelia, basal lamina), tubes
(e.g. vessels, bronchioles, glands), branches (e.g. blood
and lymphatic vessels, lung, kidney and mammary
epithelia), folds (e.g. dermal papillae, intestinal villae),
and bends (e.g. vessels).
Form is often viewed as the output of a biological process
but it also directly affects cellular behavior, in part by
controlling the magnitude and distribution of mechanical
stresses within the tissue [18]. For example, angiogenesis is believed to occur preferentially at the convex walls
of microvessels where mechanical forces are often greatest in vivo [19]. As we and others have shown through
manipulating the shapes of cultured cells, form also exerts
a strong effect on cellular behavior in vitro: the shape of a
cell controls several functions, including proliferation,
apoptosis, glucose metabolism, RNA processing, tissuespecific gene expression and differentiation, and stem cell
commitment [20–28]. Similarly, individual cells within a
contiguous aggregate display different behaviors that
result from the interplay between cellular location, overall
aggregate shape, and mechanical forces [29,30,31].
Thus, form can be viewed as an independent determinant
of ECM functionality.
Schematic of soft lithography as applied to biological materials. (a)
Elastomeric poly(dimethylsiloxane) (PDMS) stamps are cured against a
photolithographically created silicon master. Peeling the stamp leaves a
bas-relief of the original pattern. (b) PDMS can then be coated with ECM
and stamped against a solid substratum to transfer the protein
(microcontact printing), sealed against a solid substratum to create
channels into which a liquid solution of ECM is perfused (microfluidics),
or used as a mold against which ECM hydrogels are cured
(micromolding).
Methods for patterning ECMs
To build in vitro systems that faithfully reproduce the
structure of tissues probably requires the synthesis of
ECMs with microscale heterogeneity. To date, several
synthetic schemes have been developed to form 2D patterns of matrix proteins on rigid substrata. Early work used
photolithography — a light-based patterning technique
akin to high-resolution photography — to indirectly control where proteins could adsorb on glass or silicon [32].
More recently, ‘soft’ lithographic techniques, originally
developed by Whitesides and colleagues [33], that use
elastomeric stamps to pattern ECM have grown in popularity, largely because of ease of use (Figure 1). Patterning
usually takes place through contact printing or adsorption
in microfluidic channels; with stamps that have multiple
levels of features, it is possible to generate complex 2D
mosaics and gradients of ECMs [34,35]. Because cells
grown on these patterned substrata often behave differently from cells in homogeneous monolayer culture, 2D
patterns have provided a useful tool for investigating the
role of microenvironment in basic cell biology [28].
In contrast to the extensive work in 2D patterning of
adsorbed or printed ECMs, only recently have investigators focused on recapitulating the 3D architecture of
ECM gels. Initial attempts used light to photopolymerize
small organic molecules into hydrogels and required
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specialized chemistries [36]. To synthesize 3D patterned
ECMs consisting of natural proteins, we and others have
recently developed several techniques to mold macromolecular gels [37,38,39]. These methods rely on molds
that are treated so that their surfaces are non-adherent;
liquid precursors (e.g. an acid extract of type I collagen or
cold matrigel) that are gelled against these molds detach
easily to yield gels with sharply defined features with
<1 mm resolution (Figure 2a) [37].
In addition to introducing surface texture onto a gel,
lithographic techniques can be used to form monolithic
gels that contain internal surfaces, such as cavities, channels and networks (Figure 2). Formation of internal
patterns requires the use of sacrificial materials, which
are initially embedded in a gel and then removed to yield
an open internal space. Examples of such sacrificial
materials include paraffin [40], matrigel [41] and gelatin
(AP Golden and J Tien, unpublished). Another strategy
for patterning ECMs in 3D relies on stacking or direct
ink-jet printing of microstructured gels to form multilayered laminates that localize distinct populations of
cells to different planes or areas [37,42]. These methods
attempt to build ECMs and tissues layer by layer, and still
need to address issues of resolution, speed and alignment.
Current Opinion in Biotechnology 2006, 17:518–523
520 Tissue and cell engineering
Figure 2
Images of microstructured gels. (a) Arrays of posts in type I collagen.
(b) Arrays of matrigel embedded in type I collagen. (c) A cylindrical
channel in fibrin. (d) An open network in type I collagen, perfused by
a suspension of red blood cells. Scale bars refer to 100 mm in (a–c)
and 500 mm in (d). [Image in (b) adapted from [41] with permission].
Much work remains to be done to replicate the full
diversity of tissues in these in vitro systems. In particular,
the engineering of ECMs suitable for modeling tissues
with scant stroma and high cellularity (e.g. renal medulla)
remains a challenge. Nevertheless, several groups have
begun to exploit the unique architectures of these microstructured ECMs for tissue engineering and development.
ECMs for tissue engineering
A promising use of patterned ECMs lies in tissue engineering, as shown below by recent examples in engineering functional microvessels and epidermis in vitro. Efforts
in tissue engineering are currently biased towards designing synthetic biomaterials (e.g. scaffolds) and growth
factors, with the expectation that specific molecules
can direct cells seeded within them to achieve tissuespecific function and histology [43,44]. Although this
approach can form tissues with simple laminated organization (skin, cornea and arteries), it has difficulty in
forming functional complex tissues. For example, vascular endothelial cells seeded within bulk ECM gels or
synthetic polymers will form random cords, but these
cords do not coalesce into an open microvascular network,
even in the presence of large amounts of growth factors
[45]. The absence of flow in homogeneous constructs in
vitro can predispose endothelial cords to apoptosis. As a
result, several groups have used various strategies to
enhance survival of engineered microvascular tissues,
such as transfection with anti-apoptotic genes [46] and
introduction of mesenchymal cells [47].
How can microstructured ECMs help in forming functional microvessels? As originally envisioned by Vacanti
Current Opinion in Biotechnology 2006, 17:518–523
and colleagues [48], using an ECM with pre-formed
channels that could be perfused upon cell seeding would
enhance the stability of the construct. This approach
provides immediate exposure to shear stress and chemical
factors, and thus should avoid the regression observed
with cells seeded in bulk gels. Using patterned ECMs, we
have recently demonstrated that perfused endothelial
tubes remained patent for weeks without any observable
changes in cellular organization (Figure 3). These tubes
were formed by seeding endothelial cells through ECM
gels that have open channels spanning the gels [38].
Over time, these endothelial tubes developed functional
behaviors typical of microvessels in vivo, such as barrier
function and support of leukocyte adhesion. Thus, the
use of microstructured ECMs can enhance the stability
and functionality of engineered microvessels.
An appropriate 3D organization appears to play a role
beyond simply providing ready perfusion. In fact, perfusing embedded endothelial cells via interstitial flow does
not lead to formation of stable vessels (GM Price and J
Tien, unpublished). The combination of perfusion and
correct polarization, both of which stem from the presence of an open channel, may be required for stable
vessels to develop.
Use of microstructured ECMs has also led to enhanced
differentiation in engineered epidermis: Toner, Pins and
colleagues [49,50] reasoned that ECMs that mimic the
wavy geometry of rete ridges (the interdigitations
between epidermis and dermis) should provide seeded
keratinocytes with topographic cues present in native
skin, and thus should lead to more functional tissue,
compared with cells seeded on flat ECMs. To test their
hypothesis, they created a synthetic ‘basal lamina’ by
polymerizing collagen or gelatin against an undulating
silicone elastomer surface. When cultured on top of these
Figure 3
Images of perfused microvessels and microvascular networks
comprised of microstructured type I collagen gels and human dermal
microvascular endothelial cells. (a) An eight-day-old endothelial tube.
(b) A solution of fluorescently labeled albumin, perfused through a
five-day-old endothelial tube. The cells form a strong barrier that
confines the protein to the luminal compartment. (c) A six-day-old
patterned microvascular network. Scale bars refer to 100 mm.
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Extracellular matrix applications Nelson and Tien 521
ECM membranes, keratinocytes conformed to the micrometer scale ridges on the surface and showed enhanced
stratification and expression of differentiation markers in
deep undulations.
Figure 4
ECMs for the study of development
A second application of patterned ECMs is in the study of
tissue development. A better understanding of the
mechanisms that direct development and functional differentiation will not only suggest strategies to treat developmental defects, but will also advance efforts to
engineer complex, functional tissues. A large subset of
tissues and organs — kidney, lung, pancreas and prostate,
salivary and mammary glands — develop by a process
called branching morphogenesis [51]. This process starts
with local invagination of an epithelial sheet to form a
primary placode or bud [52]. This primary structure then
undergoes reiterative bifurcation and/or lateral branching
at non-random sites. The specific distribution of branch
sites and lengths is unique for each tissue and generates
tissue-specific 3D geometries.
How can microstructured ECMs aid in the study of
development? Culture models developed by Bissell
and colleagues [53] and in vivo studies have established
that morphogenesis and functional differentiation of
epithelial cells are both critically dependent on the
ECM, and have proven the importance of three-dimensionality in biological signaling [54]. In particular, collagen and fibronectin fibrils accumulate at sites of clefting
and branching in embryonic salivary gland, lung and
kidney [55–59]. Despite the recognition that branching
morphogenesis takes place in a complex heterogeneous
3D ECM, the biochemical requirements for branching in
the mammary gland have been defined using in vitro
models of mammary epithelial cells cultured within
homogeneous gels of collagen I or matrigel [60–62].
These models have helped determine the signals that
are absolutely required for branching to occur. Nevertheless, cells in homogeneous gels branch randomly
rather than in the characteristic arborized pattern of the
gland in vivo. Use of these gels has thus provided a limited
understanding of the signals that determine sites of
branching in the mammary gland and other organs.
We and others have recently begun to use microstructured ECMs to examine how the placement of epithelial
cells can, by itself, control the development of form
[18,29,63]. Numerical simulations and experimental
cultures both suggest that the form of the pre-existing
tissue instructs several of the symmetry-breaking events
during morphogenesis [29,64], a concept introduced as
early as the late 1800s by Wilhelm His [65]. For instance,
by culturing cells on large (100–1000 mm) 2D islands of
ECM, it was found that whether individual cells within an
epithelial sheet proliferate depended on their position
within the sheet and its overall geometry [29]. Slight
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Images of proliferation and invasion in structured ECMs. (a) Phase
contrast image of cells cultured on 2D pattern of asymmetric (off-center)
annulus pattern. (b) Colorimetric image of proliferation on 2D
asymmetric pattern, generated by stacking images from 50 samples to
show the frequency of cells proliferating as a fuction of space. A pixel
value of 0.20 indicates that 20% of cells at that location proliferated.
(c) Abrogation of shape-induced selectivity in proliferation by disruption
of cell–cell adhesion using a dominant-negative cadherin construct.
Proliferation becomes more uniform across the monolayer with this
treatment. (d) Epithelial cells cultured within cubic cavities migrate
specifically from the vertices. Scale bars refer to 100 mm in (a–c) and 50
mm in (d). [Images in (a–c) reproduced from [29] with permission,
copyright 2005, National Academy of Sciences, USA.]
asymmetry in the shape of the sheet of cells altered the
pattern of proliferation (Figure 4). These events require
integrity of the cellular sheet, because disrupting connections between the cells leads to unpatterned proliferation. We speculate that, in 3D, these spatial variations
induce feed-forward events that magnify and preserve an
original slight heterogeneity so that a stable, complex
tissue can emerge. To test this hypothesis, we have
studied the response of epithelial cells within patterned
cavities in collagen gels to morphogens. Stereotyped sites
of invasion developed in these 3D cultures, indicating
that tissue structure not only affects proliferation, but
migration as well (CM Nelson and MJ Bissell, unpublished). These results suggest that the 3D architecture of
a tissue can alter further morphogenesis and support the
idea that form should be viewed as an independent
effector of development. Microstructured ECMs thus
allow us to address how form affects its own evolution
in the presence of morphogens.
Conclusions
The development of methods to deliberately introduce
microscale variations in culture models has enabled the
possibility of testing how ECM aids in the proper
Current Opinion in Biotechnology 2006, 17:518–523
522 Tissue and cell engineering
development of tissue form and function. ECM is not
simply a glue that binds cells into tissues, nor is it just a
reservoir of immobilized growth factors, proteases and
matrix proteins. Heterogeneity in the ECM — whether in
terms of geometry or chemical composition — appears to
provide signals designed to integrate the behavior of
populations of cells across large distances. Although in
their infancy, the applications of microstructured ECMs
to the study of tissue engineering and development seem
especially promising, and could one day lead to a rational,
quantitative description of morphogenetic processes. In
retrospect, it is not surprising that, even in a material as
well studied as type I collagen [16], there are ways to
enhance functionality simply by adding structure.
Acknowledgements
CMN is a postdoctoral fellow in Mina Bissell’s laboratory. Our work was
supported by grants from the Department of Defense (W81XWH-04-10582 to CMN and DAMD17-02-1-438 to MJB), the National Institute of
Biomedical Imaging and Bioengineering (EB002228 and EB003157 to
JT), the National Cancer Institute (CA64786 and CA57621 to MJB), the
Whitaker Foundation (RG-02-0344 to JT), and a Boston University
Provost’s Innovation Award (to JT). We would especially like to thank
Mina Bissell for her encouragement.
References and recommended reading
Papers of particular interest, published within the annual period of
review, have been highlighted as:
of special interest
of outstanding interest
1.
Young B, Heath JW: Wheater’s Functional Histology: A Text and
Colour Atlas. Churchill Livingstone; 2000.
2.
Vracko R: Basal lamina scaffold–anatomy and significance for
maintenance of orderly tissue structure. Am J Pathol 1974,
77:314-346.
3.
4.
Murray CD: The physiological principle of minimum work
applied to the angle of branching of arteries. J Gen Physiol
1926, 9:835-841.
Nelson CM, Bissell M: Of extracellular matrix, scaffolds, and
signaling: Tissue architecture regulates development,
homeostasis, and cancer. Annu Rev Cell Dev Biol 2006,
22:287-309.
5.
Kessel RG, Kardon RH: Tissues and Organs: A Text-Atlas of
Scanning Electron Microscopy. WH Freeman; 1979.
6.
Hay ED (Ed.): Cell Biology of Extracellular Matrix. Edited by Hay ED.
Plenum Press; 1991.
7.
Folkman J, Klagsbrun M, Sasse J, Wadzinski M, Ingber D,
Vlodavsky I: A heparin-binding angiogenic protein–basic
fibroblast growth factor is stored within basement membrane.
Am J Pathol 1988, 130:393-400.
8.
Aszodi A, Pfeifer A, Wendel M, Hiripi L, Fassler R: Mouse models
for extracellular matrix diseases. J Mol Med 1998, 76:238-252.
9.
Colognato H, Yurchenco PD: Form and function: the laminin
family of heterotrimers. Dev Dyn 2000, 218:213-234.
10. Ross R: Wound healing. Sci Am 1969, 220:40-50.
11. Skalen K, Gustafsson M, Rydberg EK, Hulten LM, Wiklund O,
Innerarity TL, Boren J: Subendothelial retention of
atherogenic lipoproteins in early atherosclerosis.
Nature 2002, 417:750-754.
12. Dvorak HF: Tumors: wounds that do not heal. Similarities
between tumor stroma generation and wound healing.
N Engl J Med 1986, 315:1650-1659.
Current Opinion in Biotechnology 2006, 17:518–523
13. Toole BP, Wight TN, Tammi MI: Hyaluronan-cell interactions in
cancer and vascular disease. J Biol Chem 2002, 277:4593-4596.
14. Paszek MJ, Zahir N, Johnson KR, Lakins JN, Rozenberg GI,
Gefen A, Reinhart-King CA, Margulies SS, Dembo M, Boettiger D
et al.: Tensional homeostasis and the malignant phenotype.
Cancer Cell 2005, 8:241-254.
This paper provides the first mechanistic demonstration of how ECM
rigidity affects malignant progression.
15. Hsu S, Jamieson AM, Blackwell J: Viscoelastic studies of
extracellular matrix interactions in a model native collagen gel
system. Biorheology 1994, 31:21-36.
16. Bornstein MB: Reconstituted rat-tail collagen used as
substrate for tissue cultures on coverslips in Maximow slides
and roller tubes. Lab Invest 1958, 7:134-137.
17. Kleinman HK, McGarvey ML, Hassell JR, Star VL, Cannon FB,
Laurie GW, Martin GR: Basement membrane complexes with
biological activity. Biochemistry 1986, 25:312-318.
18. Ingber DE: Mechanical control of tissue growth: function
follows form. Proc Natl Acad Sci USA 2005, 102:11571-11572.
This paper briefly reviews the evidence that mechanical forces affect the
directional growth of tissues.
19. Hudlicka O: What makes blood vessels grow? J Physiol 1991,
444:1-24.
20. Boudreau N, Werb Z, Bissell MJ: Suppression of apoptosis by
basement membrane requires three-dimensional tissue
organization and withdrawal from the cell cycle. Proc Natl Acad
Sci USA 1996, 93:3509-3513.
21. Bissell MJ, Farson D, Tung AS: Cell shape and hexose transport
in normal and virus-transformed cells in culture. J Supramol
Struct 1977, 6:1-12.
22. Farmer SR, Ben-Ze’av A, Benecke BJ, Penman S: Altered
translatability of messenger RNA from suspended anchoragedependent fibroblasts: reversal upon cell attachment to a
surface. Cell 1978, 15:627-637.
23. Ben-Ze’ev A, Farmer SR, Penman S: Protein synthesis requires
cell-surface contact while nuclear events respond to cell
shape in anchorage-dependent fibroblasts. Cell 1980,
21:365-372.
24. Emerman JT, Burwen SJ, Pitelka DR: Substrate properties
influencing ultrastructural differentiation of mammary
epithelial cells in culture. Tissue Cell 1979, 11:109-119.
25. Roskelley CD, Desprez PY, Bissell MJ: Extracellular matrixdependent tissue-specific gene expression in mammary
epithelial cells requires both physical and biochemical signal
transduction. Proc Natl Acad Sci USA 1994, 91:12378-12382.
26. McBeath R, Pirone DM, Nelson CM, Bhadriraju K, Chen CS:
Cell shape, cytoskeletal tension, and RhoA regulate stem
cell lineage commitment. Dev Cell 2004, 6:483-495.
27. Folkman J, Moscona A: Role of cell shape in growth control.
Nature 1978, 273:345-349.
28. Chen CS, Mrksich M, Huang S, Whitesides GM, Ingber DE:
Geometric control of cell life and death. Science 1997,
276:1425-1428.
29. Nelson CM, Jean RP, Tan JL, Liu WF, Sniadecki NJ, Spector AA,
Chen CS: Emergent patterns of growth controlled by
multicellular form and mechanics. Proc Natl Acad Sci USA 2005,
102:11594-11599.
This paper provides the first evidence in vitro that the shape of an
aggregate of cells can influence preferential sites of cell division, in part
by controlling the distribution of mechanical forces in the aggregate.
30. Farge E: Mechanical induction of Twist in the Drosophila
foregut/stomodeal primordium. Curr Biol 2003, 13:1365-1377.
31. Hove JR, Koster RW, Forouhar AS, Acevedo-Bolton G, Fraser SE,
Gharib M: Intracardiac fluid forces are an essential epigenetic
factor for embryonic cardiogenesis. Nature 2003, 421:172-177.
32. O’Neill C, Jordan P, Ireland G: Evidence for two distinct
mechanisms of anchorage stimulation in freshly explanted
and 3T3 Swiss mouse fibroblasts. Cell 1986, 44:489-496.
www.sciencedirect.com
Extracellular matrix applications Nelson and Tien 523
33. Whitesides GM, Ostuni E, Takayama S, Jiang X, Ingber DE:
Soft lithography in biology and biochemistry. Annu Rev Biomed
Eng 2001, 3:335-373.
34. Tien J, Nelson CM, Chen CS: Fabrication of aligned
microstructures with a single elastomeric stamp.
Proc Natl Acad Sci USA 2002, 99:1758-1762.
50. Downing BR, Cornwell K, Toner M, Pins GD: The influence of
microtextured basal lamina analog topography on
keratinocyte function and epidermal organization. J Biomed
Mater Res A 2005, 72:47-56.
This study, along with [49], illustrates how the use of a patterned ECM
enhances the functional differentiation of epidermal keratinocytes for skin
tissue engineering.
35. Jeon NL, Dertinger SKW, Chiu DT, Choi IS, Stroock AD,
Whitesides GM: Generation of solution and surface gradients
using microfluidic systems. Langmuir 2000, 16:8311-8316.
51. Davies JA: Do different branching epithelia use a conserved
developmental mechanism? Bioessays 2002, 24:937-948.
36. Nguyen KT, West JL: Photopolymerizable hydrogels for tissue
engineering applications. Biomaterials 2002, 23:4307-4314.
52. Affolter M, Bellusci S, Itoh N, Shilo B, Thiery JP, Werb Z: Tube or
not tube: remodeling epithelial tissues by branching
morphogenesis. Dev Cell 2003, 4:11-18.
37. Tang MD, Golden AP, Tien J: Molding of three-dimensional
microstructures of gels. J Am Chem Soc 2003,
125:12988-12989.
38. Chrobak KM, Potter DR, Tien J: Formation of perfused,
functional microvascular tubes in vitro. Microvasc Res 2006,
71:185-196.
This study demonstrates how the use of a patterned ECM enables tissue
engineering of functional microvessels.
39. Cabodi M, Choi NW, Gleghorn JP, Lee CS, Bonassar LJ,
Stroock AD: A microfluidic biomaterial. J Am Chem Soc 2005,
127:13788-13789.
40. Vernon RB, Gooden MD, Lara SL, Wight TN: Native fibrillar
collagen membranes of micron-scale and submicron
thicknesses for cell support and perfusion. Biomaterials 2005,
26:1109-1117.
41. Tang MD, Golden AP, Tien J: Fabrication of collagen gels that
contain patterned, microscale cavities. Adv Mater 2004,
16:1345-1348.
42. Odde DJ, Renn MJ: Laser-guided direct writing for applications
in biotechnology. Trends Biotechnol 1999, 17:385-389.
43. Lutolf MP, Hubbell JA: Synthetic biomaterials as instructive
extracellular microenvironments for morphogenesis in tissue
engineering. Nat Biotechnol 2005, 23:47-55.
This paper thoroughly reviews the potential of using chemistry to design
new materials for tissue engineering.
44. Levenberg S, Langer R: Advances in tissue engineering.
Curr Top Dev Biol 2004, 61:113-134.
45. Montesano R, Pepper MS: Three-dimensional in vitro assay of
endothelial cell invasion and capillary tube morphogenesis. In
Vascular Morphogenesis: In Vivo, In Vitro, In Mente. Edited by Little
CD, Mironov V, Sage EH. Birkhaüser; 1998:79-110.
53. Schmeichel KL, Bissell MJ: Modeling tissue-specific signaling
and organ function in three dimensions. J Cell Sci 2003,
116:2377-2388.
54. Abbott A: Cell culture: biology’s new dimension. Nature 2003,
424:870-872.
55. Sakai T, Larsen M, Yamada KM: Fibronectin requirement in
branching morphogenesis. Nature 2003, 423:876-881.
56. Fukuda Y, Masuda Y, Kishi J, Hashimoto Y, Hayakawa T,
Nogawa H, Nakanishi Y: The role of interstitial collagens
in cleft formation of mouse embryonic submandibular
gland during initial branching. Development 1988,
103:259-267.
57. Wicha MS, Liotta LA, Vonderhaar BK, Kidwell WR: Effects of
inhibition of basement membrane collagen deposition on rat
mammary gland development. Dev Biol 1980, 80:253-256.
58. Silberstein GB, Daniel CW: Glycosaminoglycans in the basal
lamina and extracellular matrix of the developing mouse
mammary duct. Dev Biol 1982, 90:215-222.
59. Silberstein GB, Strickland P, Coleman S, Daniel CW: Epitheliumdependent extracellular matrix synthesis in transforming
growth factor-b1-growth-inhibited mouse mammary gland.
J Cell Biol 1990, 110:2209-2219.
60. Brinkmann V, Foroutan H, Sachs M, Weidner KM, Birchmeier W:
Hepatocyte growth factor/scatter factor induces a variety of
tissue-specific morphogenic programs in epithelial cells.
J Cell Biol 1995, 131:1573-1586.
61. Soriano JV, Pepper MS, Nakamura T, Orci L, Montesano R:
Hepatocyte growth factor stimulates extensive development
of branching duct-like structures by cloned mammary gland
epithelial cells. J Cell Sci 1995, 108:413-430.
46. Enis DR, Shepherd BR, Wang Y, Qasim A, Shanahan CM,
Weissberg PL, Kashgarian M, Pober JS, Schechner JS: Induction,
differentiation, and remodeling of blood vessels after
transplantation of Bcl-2-transduced endothelial cells. Proc
Natl Acad Sci USA 2005, 102:425-430.
62. Simian M, Hirai Y, Navre M, Werb Z, Lochter A, Bissell MJ:
The interplay of matrix metalloproteinases, morphogens and
growth factors is necessary for branching of mammary
epithelial cells. Development 2001, 128:3117-3131.
47. Koike N, Fukumura D, Gralla O, Au P, Schechner JS, Jain RK:
Creation of long-lasting blood vessels. Nature 2004,
428:138-139.
63. Huang S, Brangwynne CP, Parker KK, Ingber DE: Symmetrybreaking in mammalian cell cohort migration during tissue
pattern formation: role of random-walk persistence.
Cell Motil Cytoskeleton 2005, 61:201-213.
48. Kaihara S, Borenstein J, Koka R, Lalan S, Ochoa ER, Ravens M,
Pien H, Cunningham B, Vacanti JP: Silicon micromachining to
tissue engineer branched vascular channels for liver
fabrication. Tissue Eng 2000, 6:105-117.
64. Shraiman BI: Mechanical feedback as a possible regulator
of tissue growth. Proc Natl Acad Sci USA 2005,
102:3318-3323.
49. Pins GD, Toner M, Morgan JR: Microfabrication of an analog of
the basal lamina: biocompatible membranes with complex
topographies. FASEB J 2000, 14:593-602.
65. His W: Unsere Körperform und das physiologische Problem ihrer
Entstehung. Leipzig: F.C.W. Vogel; 1874. [Translation: Our body
form and the physiological problem of its development.]
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Current Opinion in Biotechnology 2006, 17:518–523